Method of forming a double container and related assembly

ABSTRACT

A double container, structure for use in forming a double container, and related method are disclosed. The double container may be formed by connecting first and second open-ended containers in a generally opposed relationship. In the preferred embodiment, pairs of matching projections extend from the end wall of each container. One or both projections on one container may include a melting area or region that is placed in contact with the corresponding projection on the opposite container. Ultrasonic energy is then supplied to melt the melting area or region as the containers are pressed together. Upon solidification, a bond is thus formed between the projections to create the double container. In a second embodiment, an intermediate structure for receiving a second container is attached to the first container, such as by ultrasonic welding.

TECHNICAL FIELD

[0001] The present invention is directed to the container art and, more particularly, to a method for easily, reliably, securely, and inexpensively securing one container to another and the resulting assembly.

BACKGROUND OF THE INVENTION

[0002] The use of molded plastic containers continues to grow in the consumer market at a rapid rate and promises to continue in years to come. For many products, such as liquid or semi-liquid (viscous) cosmetics or the like, the plastic container, such as a bottle or jar, is by far the most popular. Advantageously, a plastic container is not only non-breakable, but can be molded into different shapes so as to be very attractive, as well as functional. In addition, from a cost standpoint, the use of plastic is competitive with the other materials often used to form containers, such as glass.

[0003] One of the most popular containers used for cosmetics, as well as other liquid and semi-liquid products, is the blow molded bottle or jar. Usually, such a bottle or jar is fabricated of a clear, translucent or opaque plastic material. For example, polyethylene terephthalate (PET) with additives for varying light transmission and/or color is used to form most types of cosmetic containers. Of course, other materials can also be chosen depending on various factors, such as the type of product contained, the desired size or shape of the container, the expected or required service life, any recycling/environmental considerations, or inherent cost constraints.

[0004] In addition to containing the product, the container should have an appearance that is pleasing to the eye, since the aesthetics may ultimately influence the customer's decision to select one product over another and/or consummate the purchase. As noted above, the attractiveness of the container may be significantly enhanced by forming it having a distinctive or irregular shape, as well as by using eye-catching colors and intricate surface patterns or designs. Many different types of containers embodying some or all of these features are well known in the art, and are commonly used as part of an overall marketing strategy in an effort to boost sales over the competition.

[0005] One particular arrangement that has been found to have success from a marketing standpoint is the “double” container, in which a first container holding a first substance (e.g., nail polish) is fixedly attached to a second container holding a second, related substance (e.g., nail polish overcoat). In one possible manner of forming this double container, the first container is attached to an intermediate, open-ended structure having an internally threaded opening for receiving the open end of a second, adjacent container. While the result in a double container that it suitable for use in the intended way, the coupling of the intermediate structure to the first container usually requires the use of separate connector parts or couplers, which is deleterious in terms of cost and complexity.

[0006] Accordingly, a need is identified for a method of forming a double container in a less complex and less expensive manner than is presently employed. Specifically, the double container would be easy to construct using separate structures, such as containers, formed by well-known techniques, such as blow molding. The structures would also be held together to form the resulting assembly in a secure fashion, including without the need for extra connecting parts or the like.

SUMMARY OF THE INVENTION

[0007] In accordance with a first aspect of the invention, an assembly for intended use in forming a double container is provided. The assembly comprises a first open-ended structure having a first projection extending from an outer surface thereof and a second open-ended structure including a second projection having at least one area or region adapted for melting formed along an outer surface thereof. The first projection contacts the melting area or region when the first and second structures are positioned with the open ends thereof in a generally opposed relationship such that a bond is formed therebetween when the area or region is at least partially melted and then solidified.

[0008] In one embodiment, the first and second structures are containers, each of which may be blow-molded from a preform or parison fabricated of the same material (e.g., PET). Each container may include a threaded neck for receiving a closure. The melting area or region is preferably provided on a vertically extending side surface of the first projection, such that a shear joint is formed between the first and second projections upon solidification of the melting area or region. The first container may include a pair of first projections and the second container may include a pair of second projections. The first and second pairs of projections preferably match and align when the containers are positioned in the generally opposed relationship. In the preferred embodiment, each pair of projections comprises first and second generally parallel ribs projecting from a surface of the corresponding container opposite the open end thereof. The projections may extend substantially the same distance from the corresponding surface of each container.

[0009] The first container may include a first seating surface and the second container may include a second seating surface. The seating surfaces are adapted for making contact with one another when the bond is formed between the first and second containers. Preferably, the first and second seating surfaces surround the first and second projections.

[0010] In another embodiment, the first structure is a container and the second structure is an intermediate structure including a receiver for receiving a portion of a second container. Preferably, the receiver is a threaded opening for at least partially receiving a correspondingly threaded neck of the second container.

[0011] In accordance with a second aspect of the invention, a method of forming an assembly for use in forming a double container is disclosed. The method comprises: (1) positioning first and second open-ended structures in a generally opposed relationship; (2) at least partially contacting a first projection on the first structure with a melting area or region on the second structure; and (3) supplying ultrasonic energy to the first projection such that the melting area or region at least partially melts and forms a bond between the structures. Preferably, the second structure includes a second projection on which the melting area or region is formed and the contacting step includes at least partially contacting the first projection with the melting area or region on the second projection. The supplying step may include: (1) inserting an ultrasonic transmitter into the opening of the first structure and into contact with a surface thereof; (2) supplying ultrasonic energy in the range of about 10-40 kHz; and (3) holding the first projection in at least partial contact with the melting area or region for at least 0.2 seconds. The method may include using a stable support structure for supporting the second structure prior to contacting the first projection with the melting area or region. In the case where the first structure is a container and the second structure is an intermediate structure including a receiver, the method may further include placing a portion of a second container in the receiver to form a double container.

[0012] In accordance with a third aspect of the invention, a structure for use in forming a double container assembly for the intended use of holding a first substance and a second related substance in first and second separate chambers is disclosed. The container comprises a first open-ended body including a first projection extending from an outer surface of an end wall thereof and having an area or region adapted for melting formed along a vertical side surface thereof. Accordingly, a portion of a second structure may contact the melting area or region such that a bond is formed therebetween when the area or region is at least partially melted and then solidifies. The first and second structure maybe containers. Alternatively, the first structures may be an intermediate structure for attachment to a first container including a receiver for receiving a portion of a second container.

[0013] In one embodiment, a second projection including a melting area or region may also be provided on the end wall. The first and second projections may be oriented generally parallel to each other. An annular projection including a seating surface adapted for engaging a portion of the second structure may also be formed along an end wall of the first structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a cross-sectional side view showing one possible example of a double container or container assembly formed in accordance with the present invention;

[0015]FIG. 2 is an enlarged, partially cutaway, cross-sectional side view depicting the manner in which two containers are connected in a preferred embodiment of the present invention;

[0016]FIG. 3 is a bottom view showing an example of one type of container that may be used in forming the double container or container assembly of the present invention;

[0017]FIG. 4 is an enlarged, partially cutaway, cross-sectional side view showing the connection formed between the two containers;

[0018]FIG. 5 is a cross-sectional side view showing one possible embodiment of the double container;

[0019]FIGS. 6a, 6 b, and 6 c are perspective views showing examples of the various shapes of double containers that may be formed using the techniques disclosed herein; and

[0020]FIG. 7 is a cross-sectional side view showing an alternate embodiment of the double container.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] With reference to FIG. 1, a double container or container assembly 10 constructed according to a preferred embodiment of the invention is disclosed. The assembly includes at least two open ended structures, such as containers 12, 14, each having an internal chamber C₁, C₂ for receiving a substance, such as a food product, cosmetic product, or the like (not shown). One or both containers 10, 12 may be formed from a preform (not shown) using well-known blow molding techniques. As is known in the art, the preform may be formed of polyethylene terephthalate (PET), polycarbonate (PC), and/or other rigid or semi-rigid plastic materials or synthetic resins (see below), possibly with additives for varying light transmission, color, strength, or other characteristics. Of course, other like materials may also be used to form the preform, depending on, among other things, the size and shape, inherent cost limitations, the required service life, and the particular type and amount of product being contained (liquid, semi-liquid, or even dry).

[0022] The preform is typically tubular in shape, being completely open at one end (usually the upper end), hollow in the middle, and closed at the opposite end (usually the lower end or bottom). As will be readily appreciated by those skilled in the art, the upper end of the preform becomes the neck N₁ or N₂ defining the opening or receiver of the resulting container 12 or 14. The neck N₁, N₂ of each container 12, 14 in FIG. 1 is shown as being relatively short and threaded for receiving a corresponding cap or closure E. However, the use of different sizes, shapes or types of necks, if any, is entirely possible.

[0023] In accordance with one aspect of the invention, one of the containers 12, 14 is provided with at least one projection for engaging a melting area or region on the other container when the two are positioned in a generally opposed relationship (that is, with the open ends facing in generally opposite directions). To demonstrate a preferred manner of connecting the two containers 12, 14 together, reference is now made to FIG. 2, which shows the first container 12 having a pair of spaced projections, such as a first pair of ribs 16 a, 16 b. As perhaps best understood with reference to FIG. 3, the first pair of ribs 16 a, 16 b extend generally parallel to each other in the same direction and project from an outer surface of the end wall 12 a the first container 12. Each rib 16 a, 16 b of the first pair includes a melting area or region 18 a, 18 b, preferably in the form of a projection provided on or along opposed an outer vertical side surface thereof. In the case where the container 12 is blow molded, the first pair of ribs 16 a, 16 b and the melting area or region 18 a, 18 b on each are preferably integrally formed along the corresponding end thereof during the process used to form the corresponding preform (e.g., during injection molding). However, in the case where the container 12 or 14 itself is injection molded, these structures may of course be integrally formed during that process as well.

[0024] A corresponding pair of mating projections, such as a second spaced pair of ribs 20 a, 20 b are provided on the second container 14. To mate and align with each of the first pair of ribs 16 a, 16 b when the containers 12, 14 are positioned in a generally opposed relationship, the second pair of ribs 20 a, 20 b also extend generally parallel to each other in the same direction and project from an outer surface 14 a of the second container 14. As should be appreciated, the spacing between the second pair of ribs 20 a, 20 b is such that when the containers 12, 14 are brought together, as shown in FIG. 2, the upper end of each rib 20 a, 20 b at least partially contacts or engages the corresponding melting area or region 18 a, 18 b associated with the first container 12, which as described above is preferably formed on an opposed vertical side surface of each of the first pair of ribs 16 a, 16 b.

[0025] To connect the two containers 12, 14 and form the double container assembly 10 of the present invention using a preferred embodiment of the method disclosed herein, the second container 14 is positioned on a stable support structure, such as an elongated mounting fixture or jig 22. At least a portion of the jig 22 is preferably sized for passing axially through the open end of the container 14, such as the passage defined by neck N₂ in the embodiment shown in FIG. 2. Indeed, it is preferable to provide the jig 22 with a width dimension D that closely matches that of the opening through which it is inserted into chamber C₂. This helps to stabilize the container 14 by preventing it from moving radially when positioned on the jig 22. It is also preferable to provide the jig 22 with an end face 22 a that matches the contour of the corresponding portion of the container 14, such as the inside surface of the end wall 14 a. In the simplest case, as shown in FIG. 2, the end face 22 a of the jig 22 is flat, as is the inner surface of the end wall 14 a of the second container 14. However, in the case where the inner surface of the end wall 14 a is contoured (e.g., concave, convex, a combination of the two, etc.), the end face 22 a of the jig 22 is preferably shaped for making at least partial contact therewith.

[0026] Once the second container 14 is in position on the jig 22, the first container 12 is brought into position such that: (1) the first pair of ribs 16 a, 16 b match and align with the second pair of ribs 20 a, 20 b; and (2) at least partial contact or engagement is established at the interface between the melting area or region 18 a, 18 b (which, in the preferred embodiment, is approximately one third as wide as the corresponding rib) and the end face of each rib 20 a, 20 b. An ultrasonic energy transmitter, such as a “welding” horn 24, or other device for transmitting ultrasonic energy is then brought into direct contact with an adjacent portion of the first container 12. As is known in the art, the contact or engagement between the end face 24 a of the horn 24 is preferably made with a portion of the first container 12 having a corresponding shape. For example, as shown in FIG. 2, the horn 24 includes a flat end face 24 a for mating with the corresponding substantially planar inner surface of the end wall 12 a of the first container 12 adjacent to the ribs 16 a, 16 b. This, of course, improves the transmission of the ultrasonic energy to the interface between the melting area or region 18 a, 18 b and the corresponding rib 20 a, 20 b. Nevertheless, other configurations besides planar-planar contact are possible, and it should be appreciated that, even in the case where a planar portion of the inner surface is adapted for engaging the end face 24 a of the horn 24, other portions of the end wall 12 a of the first container 12 need not be planar or have any particular contour.

[0027] The ultrasonic welding horn 24 is typically formed of a relatively inert, durable metal, such as titanium. In use, the horn 24 is connected to a source of ultrasonic energy, which is shown schematically and identified by reference numeral 26 in FIG. 2. Ultrasonic energy is supplied to the horn 24 from the source 26 while pressure is applied to the first container 12 (such as in the direction of arrow A in FIG. 2 in the case where the containers 12, 14 are vertically oriented and opposed). Pressure and energy are supplied at certain predetermined amounts (e.g., 10-40 kHz for 0.2-1.0 seconds) such that the melting area or region 18 a, 18 b on each first rib 16 a, 16 b liquefies or melts at the interface where at least partial contact is made with the second projection 20 a, 20 b. As a consequence of the combined melting and pressure, the each second rib 20 a, 20 b moves into at least partial, and preferably full engagement and registration with the corresponding first rib 16 a, 16 b such that a strong, secure bond is formed therebetween by the liquefied material upon solidification. As shown in FIG. 2, it is preferable to make the contact between the corresponding ribs 16 a, 20 a, 16 b, 20 b such that the vertical side faces thereof make contact and form a shear joint 28 a, 28 b at each interface upon solidification (see FIGS. 1 and 2b). The shear joints 28 a, 28 b form a strong, secure bond, fully able to resist the application of moderate tensile, torsional, or shear forces applied to one or both containers 12, 14. Thus, using the technique described above, double container assembly 10 with separate chambers C₁, C₂ may be formed in a matter of seconds without the need for the separate connector components or expensive manufacturing processes prevalent in prior art proposals.

[0028] As perhaps best shown in FIG. 4, the height of each rib 16 a, 16 b, 20 a, 20 b in the vertical direction is preferably such that it makes contact with or is otherwise closely adjacent to the corresponding outer surface of the end wall 12 a, 14 a of each container 12, 14. Optionally, matching seating surfaces may also be provided on each container 12, 14. For example, in the version shown in FIG. 1, the first container 12 is provided with an annular projecting portion 30 having an end face 30 a that matches the end face 32 a of a corresponding projecting portion 32 on the second container 14 (see FIG. 3). Thus, when the two containers 12, 14 are interconnected as shown in FIG. 4, the end faces 30 a, 32 a mate and provide seating surfaces for each other. In the case where the material forming the projections 30, 32 is substantially opaque, the interface created serves to obscure the shear joints 28 a, 28 b and the corresponding structures forming them to provide the illusion that the two containers 12, 14 are simply one continuous container. To further enhance the illusion, the projections 30, 32 may be provided along the periphery of the end wall 12 a, 14, substantially flush with the sidewalls of the containers 12, 14 (see FIGS. 5 and 6a-6 c).

[0029] The projections 30, 32 may be continuous and annular, as described above, or may simply be intermittent. For example, in the case where the end walls 12 a, 14 b of the containers 12, 14 have square cross-sections, instead of a continuous square or circular annular projection, four separate projections (not shown) may be provided, one of which may be associated with each corner. A myriad of other configurations are possible, and it is reiterated that providing matching seating surfaces is entirely optional.

[0030] While the first and second containers 12, 14 are shown as being identical, it should be appreciated that both may be different in shape, size, style, color, material, or any other characteristic. Preferably, the two containers 12, 14 are made of the same material and one that is capable of being liquefied or melted using ultrasonic energy (PET, PC, cyclo-olefin polymer (COP), polypropylene (PP), etc.). Of course, the material chosen may depend on the contents of the container. For example, while PET can be used in a container for holding top coat, it should not be used to form one for holding nail polish because of the potential chemical reaction between the substances. Thus, in the case where nail polish is to be held in one COP container, such as the first container 12, it makes sense to also form the other, or second container 14 from COP.

[0031] A second embodiment of the double container 10 is shown in FIG. 5. As should be appreciated by making a comparison with FIG. 1, the primary difference is that the matching projections 30, 32 are coextensive with the sidewalls 12 b, 12 c of the corresponding container 12, 14. This eliminates the space S that would otherwise be formed between the outer edge of the projections 30, 32 and the sidewalls 12 b, 12 c; 14 b, 14 c (see FIG. 1). In the case where the projections 30, 32 are annular, this assists in hiding the connections (e.g., shear joints 28 a, 28 b) from view and helps to create the illusion that the double container 10 is formed of a single piece of material, instead of two separate containers 12, 14 attached together in an opposed relationship.

[0032]FIGS. 6a, 6 b, and 6 c show examples of various shapes of double containers 10 formed using the techniques disclosed herein. FIG. 6a shows a perspective view of the generally square container of FIG. 5, with a correspondingly shaped closure or end cap E provided on each container 12, 14 of the double container 10. FIG. 6b shows a similarly formed cylindrical shaped double container 10 with correspondingly shaped closures E. FIG. 6c is an example of a double container 10 formed in the shape of a truncated cone (frustoconical). As should be appreciated, each component forming the container assembly 10 in FIG. 6c (closure E₁ for first container 12, first container 12, second container 14, and closure E₂ for second container 14) is progressively larger in diameter from one end to the other. This effect may also be achieved using square closures E and containers 12, 14, or ones with sloping outer sidewalls. The point is that many different shapes and sizes of double containers 10 may be formed, depending on the particular aesthetic appearance desired.

[0033] In accordance with a second aspect of the invention, another manner of forming a double container 10 is shown in FIG. 7. In this embodiment, the first container 12 is provided with an end wall 12 a from which projections or ribs 16 a, 16 b extend. However, the corresponding projections or ribs 20 a, 20 b are formed on an intermediate open-ended structure 40, with the open end preferably comprising a receiver 42 for receiving a portion of the second container 14. At least one of each set of ribs 16 a, 16 b; 20 a, 20 b is provided with a melting area or region 18 a, 18 b, which is depicted as being formed along the vertical side face thereof. However, as described above, alternate arrangements are possible. In any case, it is preferred that each melting area or region 18 a, 18 b is integrally formed, and the material used to form the intermediate structure 40 is compatible with that of the container 12 (e.g. PET/PET, COP/COP, PP/PP, PC/PC). Matching projections 30, 32 may also be provided in container 12 and intermediate structure 40, as described above with respect to the embodiment shown in FIGS. 1 and 5. In FIG. 7, the projections 30, 32 are shown as being generally annular, but as described above, other configurations are possible.

[0034] To form the double container 10, the intermediate structure 40 is connected to the first container 12 and then the second container 14 is connected to the intermediate structure. In particular, the intermediate structure 40 may be positioned on a stable support structure, such as a jig (not shown), and the first container 12 may be positioned such that contact is made between at least one melting area or region 18 a or 18 b and the corresponding portion of the second container 14 (such as rib 20 a or 20 b). Ultrasonic energy is then transmitted to the corresponding projection(s) to form a bond, such as by melting at least one and preferably both of the melting areas or regions 18 a or 18 b and then allowing the melted material to solidify. The ultrasonic energy may be supplied through a horn 24 inserted through the opening of the container 12, substantially as described above, at a frequency and for a period of time and pressure necessary to form the bond at the interface established with the intermediate structure 40. When fully assembled in the manner shown in FIG. 7, the matching projections 30, 32 thus hide the connections and provide the illusion to the outside observer that the container 12 and the intermediate structure 40 are formed of a single piece of material.

[0035] As shown in FIG. 7, the receiver 42 may be threaded for receiving the correspondingly threaded neck N₂ of the second container 14. An end cap or closure E may also be placed on the first container 12 as described above to complete the assembly. Both the closure E and the intermediate structure 40 may optionally be provided with a space 44 for receiving a piece of material that serves to form a seal with the upper portion of the threaded neck N₁ or N₂ of the corresponding container 12, 14. One or both of the cap or closure E and the intermediate structure 40 may also include an elongated structure for extending into the chamber C₁ or C₂ defined by each container 12, 14. For example, in the case where nail polish or are separately held in the containers 12, 14, it may be desirable to attach an elongated tubular finger having a brush at one end to each of closure E and intermediate structure 40. To apply the substance in the first container 12 (e.g., nail polish) to a surface, closure E is removed and the brush (not shown) is used. The cap or closure E may then be returned to neck N₁ of the first container 12. In the case where the second container 14 holds a related substance, such as top coat, the subassembly defined by the closure E, container 12, and intermediate structure 40 may be removed from neck N₂ of the second container 14 and essentially used as a handle to apply the substance therein using the corresponding brush (assuming, of course, that the containers are relatively small in size). Of course, both containers 12, 14 could hold the same substances (i.e., different colors of nail polish) or even unrelated substances or materials.

[0036] Despite the depiction of certain embodiments in the drawings, obvious modifications or variations are possible in light of the above teachings. For example, while the melting area or region 18 a, 18 b is shown as being provided along the outer vertical side face of each projection 16 a, 16 b, it should be appreciated that it could also be provided on the end face. Also, instead of being provided on the outside vertical face, the melting area or region could be provided on the inside vertical face (provided that the position of the matching projections 20 a, 20 b on the second container 12 are adjusted accordingly). Instead of pairs of projections 16 a, 16 b and 20 a, 20 b, each container could be provided with a single matching projection, either for forming a shear joint or a butt joint (in which case the melting area would be on the end face of one of the projections). Still another possibility is to provide only one of the containers 12 or 14 (or structure 40) with a single projection for engaging a melting area or region formed directly on or otherwise associated with the bottom surface of the corresponding container or structure (not shown). In this alternative embodiment, the use of matching seating surfaces 30 a, 32 a is beneficial, since the resulting butt joint would be less resistant to breaking as the result of forces acting laterally on one of the containers 12, 14, as compared to the shear joint in the preferred embodiment. While FIG. 3 shows the melting area or region 18 a, 18 b as having a particular relative size and extending along most of the corresponding rib 16 a or 16 b, it should be appreciated that a smaller area or region may be used, depending upon the particular circumstances. The important point is that the desired bond is formed when the melting area or region solidifies. Also, while the ribs 16 a, 16 b and 20 a, 20 b are shown having a rectangular cross-sectional shape, the use of other configurations is of course possible.

[0037] In one exemplary embodiment, the ribs 16 a, 16 b on the first container 12 have a height of approximately 1.8 millimeters. The melting area or region 20 a, 20 b contacts the end wall 12 a of the container 12 and extends approximately 1.0 millimeters along each rib 16 a, 16 b. The melting area or region 18 a, 18 b has a width of approximately 0.5 millimeters. Each rib 20 a, 20 b on the second container 14 has a height of approximately 2.0 millimeters. Each rib 16 a, 16 b and 20 a, 20 b has a width of approximately 1.5 millimeters.

[0038] The foregoing description is presented for purposes of illustration and description of the various aspects of the invention. The descriptions are not intended to be exhaustive or to limit the invention to the precise form disclosed. The embodiments described above were chosen to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled. 

In the claims:
 1. An assembly intended for use in forming a double container, comprising: a first open-ended structure including a first projection extending from an outer surface thereof; and a second open-ended structure including a second, matching projection having at least one area or region adapted for melting formed on, along or adjacent to an outer surface thereof; wherein at least a portion of the first projection contacts or engages the melting area or region on the second projection when the first and second structures are positioned with the open ends thereof in a generally opposed relationship such that a bond is formed therebetween when the area or region is at least partially melted and solidified.
 2. The assembly according to claim 1, wherein the first and second structures are containers.
 3. The assembly according to claim 1, wherein the melting area or region is provided on a vertically extending side surface of the first projection, whereby the bond is in the form of a shear joint formed between the first and second projections.
 4. The assembly according to claim 1, wherein the first structure is a first container including a pair of first projections and the second structure is a second container including a pair of second projections, wherein the first and second pairs of projections match and align when the containers are positioned in the generally opposed relationship.
 5. The assembly according to claim 4, wherein each pair of projections comprises first and second generally parallel ribs projecting from a surface opposite the open end of the corresponding container.
 6. The assembly according to claim 5, wherein the projections extend substantially the same distance from the corresponding surface of each container.
 7. The assembly according to claim 1, wherein the first structure includes a first seating surface and the second structure includes a second seating surface, wherein the seating surfaces are adapted for making contact with one another when the bond is formed between the first and second projections.
 8. The assembly according to claim 7, wherein the first and second seating surfaces surround the first and second projections.
 9. The assembly according to claim 1, wherein the first and second structures are blow-molded containers, each including an opening or receiver defined by a threaded neck for receiving a cap or closure.
 10. The assembly according to claim 1, wherein the first structure is a container and the second structure is an intermediate structure including a receiver for receiving a portion of the container.
 11. The assembly according to claim 10, wherein the receiver is a threaded opening for at least partially receiving a correspondingly threaded neck of the container.
 12. A method of forming an assembly for intended use in forming a double container, comprising: positioning first and second open-ended structures with the open ends thereof in a generally opposed relationship; at least partially contacting a first projection on the first structure with a melting area or region on the second structure; and supplying ultrasonic energy to the first projection such that the melting area or region at least partially melts and upon solidification forms a bond between the structures.
 13. The method according to claim 12, wherein the second structure includes a second projection on which the melting area or region is formed and the contacting step includes at least partially contacting the first projection with the melting area or region on the second projection.
 14. The method according to claim 12, wherein the supplying step includes: inserting an ultrasonic transmitter into the opening of the first structure and into contact with a surface thereof; supplying ultrasonic energy to the surface in the range of about 10-40 kHz; and holding the first projection in at least partial contact with the melting area or region for at least 0.2 seconds.
 15. The method according to claim 14, further including the step of using a stable support structure for supporting the second structure prior to contacting the first projection with the melting area or region.
 16. The method according to claim 14, wherein the first structure is a container, the second structure is an intermediate structure including a receiver, and the method further includes placing a portion of a second container in the receiver to form a double container.
 17. A structure for use in forming a double container assembly for the intended use of holding a first substance and a second related substance in first and second chambers, comprising: a first open-ended body having a first projection extending from an outer surface thereof in a direction generally opposite the open end, the projection including an area or region adapted for melting formed along a side face thereof; whereby a portion of a second structure may contact the melting area or region such that a bond may be formed therebetween when the area or region is at least partially melted.
 18. The structure for use in forming a double container according to claim 17, wherein a second projection including a melting area or region is provided adjacent to the first projection.
 19. The structure for use in forming a double container according to claim 18, wherein the first and second projections are oriented generally parallel to each other.
 20. The structure for use in forming a double container according to claim 17, wherein the end wall of the body includes an annular projection defining a seating surface adapted for engaging a corresponding portion of the second structure.
 21. The structure for use in forming a double container according to claim 17, wherein the open-ended body is a container or includes a receiver for receiving a portion of a container. 